Detective Chief Inspector Paul Durham, from the Norfolk and Suffolk Major Investigation Team (MIT), confirmed that following initial enquiries, the incident was now being treated as suspicious, with the focus being on a line of inquiry which suggests that the woman was forcibly pushed into the carriageway.

DCI Durham said: “Although our investigation is in its early stages, initial enquiries have given me sufficient cause for concern that this was more than just a tragic accident.

“As a result I’m appealing to anyone who was in the area at the time and may have witnessed the collision – or seen the two pedestrians shortly before the collision - to come forward, no matter how insignificant the information may seem to them.”

The man is described as white, 6ft 1, of slim build with short dark hair. He was wearing blue denim jean shorts and a grey t-shirt. The woman is described as white, 5ft 7, of slim build, with long auburn coloured hair. She was wearing a bright pink t-shirt and black knee-length leggings. It is believed that both may have been walking barefoot for some time in the general direction of King’s Lynn.

Motorists were left stunned after realising the couple they saw walking on or near to the A47 were killed soon afterwards in a crash involving two cars.

Karen Payne said: “I saw them just before this happened. And then I saw the aftermath of it on the way home and automatically knew it was them involved.”

Police were called to the eastbound carriageway of the A47 at Terrington St John shortly after 2.15pm and other emergency services arrived soon afterwards.

Magpas Helemedix confirmed they flew to the scene but were stood down shortly afterwards once it became apparent both casualties had sadly died at the scene.

Norfolk police closed the road for around10 hours following the double fatality and have launched an appeal for witnesses. They are looking especially for anyone who may have witnessed the collision or saw either the pedestrians or the vehicles prior to the incident.

Across both Twitter and Facebook there were confirmed sightings of the couple including one reference by Nick Carter to their walking and holding hands in the rain.

Mr Curtis confirmed he saw “saw two pedestrians walking on A47 earlier and thought how stupid it was. Now hearing pedestrians have been struck”.

One woman wrote: “I saw them too as they were walking; it was raining at the time. I’ve only just put two and two together after reading reports. Very sad.”

A Norfolk fire service spokesman said: “Three appliances from Wisbech and Kings Lynn attended a road traffic collision; no persons were trapped and the crews assisted the police and ambulance service.”

Mid Norfolk MP George Freeman was among those to respond to the tragedy, tweeting a snap of the EDP’s front page yesterday as he called for an early start to improvements on the A47.

“Another morning...another A47 fatality,” he tweeted. “Will write to Roads Minister with details to highlight need for dualling and upgrade”.

Anyone with information should contact the Norfolk and Suffolk MIT on 101

*There will be a news conference at 10am on Tuesday when more details will be released.